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Discussion Starter · #1 ·
Hello all, have a customer with a 2011 Cruze, 1.4T and they have been getting the run-around. They had it at another repair facility for an overheating problem (they were getting the "a/c inop let idle" message. That repair facility replaced the turbo, then the thermostat and spark plugs according to the customer. They've now brought it to me and I'll explain what I've found so far:

The car can sit and idle all day with no issues, it must be driven to get hot. At first I simply suspected a poor fill job by the previous shop and performed a good vac & fill on the system - could only get 15in of vacuum... started looking for leaks and found that the water pump was leaking. Removed the water pump and found that the impeller had actually worked down the shaft slightly and was rubbing on the inside of the water pump housing. Installed the new water pump and tried the vac and fill again - this time I got 25in vacuum! Sweet, this things fixed I'm thinking... took it on a good test drive and found that it would still climb all the way to around 258°. What was odd is that it would do that and then sometimes drop clear to 125°. At that point I believed that the Thermostat was responding very slugging (even though it was new) so I replaced the thermostat. After replacing the thermostat, the problem was now worse... It would overheat sitting in the stall, the RTC sensor was only getting to about 75° and the lower hose was cold to the touch... finally worked the air lock out and have good ETC/RTC correlation now, however I'm still venting badly at the reservoir cap. I placed a pressure tester on the cap and found that at idle I'm sitting consistently at 20psi. With RPM raised to about 2,200, my pressures cycle from about 20psi - 27psi (No venting as I have the system sealed. Pressures just follow cooling fan cycling). This is obviously the cause of my venting, but where is my pressure coming from? I suspect a head gasket as I know she has hit the 260° mark several times, however I think my pressures should stay high if that were the case. There is a slight smell of combustion gases to the coolant, but I've just replaced it all due to replacing the water pump. Any other thoughts?
 

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You can get this if there is too much coolant in the reservoir. The coolant level when cold is the top of the arrow stamped on the side of the tank. As for the water pump that should have been covered by GM up to 150K miles. This car does run up to 230F under normal operating conditions - for your comparison use. Also, the engine simply won't warm up while idling when everything is working properly.
 

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Besides it being a 2011, which generally is the most troublesome since it was the first year of the U.S. Cruze, the cooling system is probably the source of most troubles of the 1st generation Cruze, with everything from bad o-rings on the coolant reservoir cap to leaking water pumps and bad water outlets that crack at the seams. Couple that with the higher normal operating temperature of the electronically controlled thermostat compared to most cars, it is tougher on all those plastic parts.

The last time I did thermostat work on my 2012 Cruze, it probably took a couple weeks of hard driving for all the air pockets to work themselves out of the system, and for the 220ish degree operating temp to settle to "normal". In my case, I was getting a lower than normal temperature of just under 200 degrees for those two weeks or so. I never had to do a water pump on my Cruze, so I'd guess that work added an additional source of air pockets to the system.

Like obermd said, the 1st gen Cruze will not reach normal operating temp from a cold start when just idling. The engine is too small. It must be driven, and will take forever to warm up if you set the fan too high. Try replacing the reservoir cap if you are still venting there, as the o-ring is probably flattened out and not working properly.

I found that my 2012 cooling system worked more reliably when I left the coolant in the reservoir at a lower than normal level. It liked being at only about 1/4 full.
 

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I would still suspect air in the system somewhere. They can be a real pain to bleed.

If it was overheated severely at some point, it is possible the head has warped slightly. A leakdown test would go towards diagnosing this.

I found that my 2012 cooling system worked more reliably when I left the coolant in the reservoir at a lower than normal level. It liked being at only about 1/4 full.
Same here, or just slightly below that line with the arrow on it.
 

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I'm guessing the o-ring on the customer radiator cap is maybe not holding pressure. When you have the pressure tester adapter on the tank you might have a good seal, when you replace the cap you're venting due to the o-ring design.

If your using a U-View type device to pull vacuum and fill under vacuum there should be very little in terms of air pockets in the system.

There's a small line that goes out the top of the water outlet, drivers side of the block, and returns to the top of the water coolant reservoir.

Ideally with the car level, this line should be the highest point of the system, and air should be purged back to the tank.

I'd fill it under vacuum, then remove some coolant from the reservoir tank, and then start and run it with the cap off, and see if you can get coolant air blockages to come up to the top of the water outlet and out of the system.

Both you and the other shop have had this block exposed to a lot of air in replacing the water pump and the thermostat. With the heater core sitting so low in this car, you might have a heck of a time bleeding it, without pulling vacuum with a fill tool.

I'm thinking your testing the system under vacuum, so you must be filling it under vacuum as well. Hum....

There has been one person who replaced the water pump because when it failed it actually caused parts of the impeller to get stuck in the thermostat, and the water pump passages.

Early pumps I think were plastic impellers. No noticeable pieces missing from the old pump that might be in the cooling passages? Rare, given you replaced the thermostat as well..
 

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I suspect a head gasket as I know she has hit the 260° mark several times, however I think my pressures should stay high if that were the case.
I don't know about head gasket leaks, but I know leaks in general can be fickle things. Given that this is turbo car, it might only leak under boost or a specific operating temperature. (This car has variable operating temperature. The ECM controls a heater attached to the thermostat.)


There is a slight smell of combustion gases to the coolant, but I've just replaced it all due to replacing the water pump. Any other thoughts?
I'd test the coolant. If it's new coolant with combustion gasses, then that's your answer right there. Everything else is just wasting time on the clock.
 

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Discussion Starter · #7 ·
Thanks for all the feedback everyone. I tried replacing the radiator cap and lowering the fluid level. While the cap did not vent as early, the condition was still there when the pressure hit 25psi or so. My block tester kit finally showed up (couldn't find my old one?!) and i was able to prove that the headgasket has failed. I'm sure this is due to the repeated overheats that the car has seen. I'm still a little surprised just because of the symptoms, but, the block test doesn't lie. I thought for sure there was something else going on that I just wasn't seeing.
 
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